Stack solid black crud remove

[pgtips]

Hi,
I've had to replace all copper pipes into the soil stack, all corroded and leaking.
The last one finished today thank God but it was the worst, no flow, I couldn't push my finger through what was originally a 40mm hole.
The build up has been solid black, I've literally had to hack it off to get free flow again.
This has happened on all 3 I've had to do.

Is it a reaction between copper pipe and iron stack or something else.?

Is there a chemical way to remove it? as I don't want to see it again for a long time. I've used plastic pipe instead of copper so the corrosion problem is fixed.

Thank you !

 

[Mr Chibs]

What copper pipes are going into your stack?

Can you take a photo please.

 

[pgtips]

No copper pipes anymore. All looks std to me, 1970s build.
Will upload images tomorrow but anyone got info on the crud would be useful

 

[Madrab]

It depends, if it was copper waste pipes then it'll have been there for many years. If it was a 70's build then I wouldn't have thought they would have used copper though especially for large waste pipes, that was when there was the famous copper shortage so that's a surprise. Copper doesn't do well with the modern chemicals and would have had a some corrosion build up but If there was enough crud to actually fill the waste pipes I would have said that would have been more likely to have been just a general crap from the wastes build up.

Was it at the point where it entered the stack and what feeds into the stack above the outflow, if anything.

 

[pgtips]

What copper pipes are going into your stack?

Can you take a photo please.

As requested, do they help with the Q? but looking forward to replies.

1st two are of the stack with replaced pipe, there is one more behind you can't see, so 3 inlets in total. Next 2 are of the copper pipe removed.
All were leaking. The shared stack serves 2 properties, flats, so the one above was discharging into mine.. lovely!

Stack seems to be cast iron, my guess is the effluent discharge is reacting to cause solid build up which I had to hack away.

Pg

 

[Harry Bloomfield]

Are you sure that is a 1970's build, it looks as if it is very much older than that? I would suggest 1950's at the very latest.